Method for making commutators



May 26, 1 959 K. KNOLL ETAL METHOD FOR MAKING COMMUTATORS Filed Sept. 1. 1953 Fig.2

Fig. 1

United States Patent METHGD FUR MAKING COMIVIUTATORS Karl Knoll, Feucht, near Nnrnberg, and Hans-Werner Rotter and Siegfried Voll, Number-g, Germany, assignors to Siemens -St-hneliertwerke Alrtiengesellschaft, lieriiniemensstadt, Germany, a corporation of Germany Application September 1, 1953, Serial No. 377,932

Claims priority, application Germany September 4, 1952 1 Claim. (Cl. 29155.54)

This invention relates to an electric conductor insulated and embedded in metal castings, more particularly in injection die-castings.

By a method similar to the production of paper a pulp may be produced of small mica flakes obtained by comminuting the mica, which in some cases is prevoiusly heated and quenched; and such mica pulp may be manufactured like paper into foils, plates, shaped bodies, and so on. In order to prevent decomposition of the final product due to moisture, synthetic resin, silicone, or phosphoric acid may be added as binding means according to former proposals.

It is diflicult to find an insulation which resists the mechanical and thermal stresses if a metal is die-cast around and which thereafter is electrically sufficiently tight. This invention eliminates these difliculties. According to the invention the conductor is covered with a coat of small mica flakes and binding means at least along the embedded portion. Thus, the conductor may be surrounded, for example, with a foil or a jacket of this material before a metal is die-cast around or it may be painted with such a material or coated by immersing or spraying. In the latter case it is advisable to use extremely small mica flakes. They appear to have the property of arranging themselves in the coat of paint in positions parallel to the paint plane. At all events the dielectric strength of the insulating coating is not afiected by the fact that the small flakes are reduced more and more. If phosphoric acid or microcosmic salt is employed as binding means, a good adhesion is obtained on the metal, particularly on iron. Consequently, the embedded conductor is jammed tight. In some cases it is advisable to heat the coat before embedding in such manner that all gasifying or vaporizing components of the binding means may escape. By this means bubble formation along the embedded portion of the insulated conductor and consequent detachment of mica particles is avoided. In this case a binding agent, such as phosphoric acid, microcosmic salts, organic combinations of silicic acid adhere tightly between the small mica flakes in such manner that the combination will not dissolve even if water and other liquids react on it. If silicone, silicic acid ester or the like are employed as binding means the organic components seem to escape so that the residual silicic acid may produce a solid combination of the small flakes.

The invention may be employed for various purposes.

2,887,764 Patented May 26, 1959 "ice For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made to the accompanying drawings.

Figures 1 to 4 of the drawing show diagrammatically by way of example a number of embodiments of the invention.

In Figure 1 an insulated terminal conductor 1 for a motor or other electrical apparatus is to be tightly led through a cover 2, for example, of a flameproof or a moisture-proof casing. For this purpose said casing cover is provided with an aforesaid insulation coat 3 surrounding the conductor and subsequently the casing 2 is die-cast around or cast around the insulated conductor.

Figure 2 shows part of an immersion heater. The heating Wire 4 is surrounded with such a coat 3, for example, by immersing or spraying. Subsequently the metal 5 is die-cast around. Such an immersion heater or the like is particularly advantageous because the temperature gradient within the heating body is very small, since only the thin coat 3 consists of insulating material. Consequently, the heating wire 4 may not assume considerably higher temperatures than the material to be heated. It is thus protected against heating up and has a long durability.

Figure 3 shows a section of a commutator for electrical machines and other contact apparatuses such as regulators. The laminations 6 are covered face to face and at the parts having dovetails with the above-mentioned coat 3. They are arranged in a die mold and the hub 8 is die-cast in or cast in, in some case according to the centrifugal casting process. The coat 3 of the laminations 6 may be produced by spraying or immersing. In this case it covers the laminations at all sides (see Figure 4).

After completion, the insulating coatings 3 may be removed from the contact surfaces 9 and the adjacent electrical connection areas by turning them oif in a lathe.

We claim:

The method of manufacturing commutators for electrical machines comprising coating peripheral conductor laminations with a mixture of fine mica flake particles and a binding agent, casting a metallic central hub casting about and at least partly embedding said conductor laminations, and finally machining down the outer periphery of said peripheral laminations to remove the coatings therefrom.

References Cited in the file of this patent UNITED STATES PATENTS 522,718 Leonard July 10, 1894 1,416,036 Kempton May 16, 1922 1,494,939 Abbott May 20, 1924 1,533,270 Reid Apr. 14, 1925 1,750,305 Gross Mar. 11, 1930 1,878,178 Power Sept. 20, 1932 2,077,282 Strom et al. Apr. 13, 1937 2,084,263 Boughton et al. June 15, 1937 2,341,235 Palmer Feb. 8, 1949 2,656,403 Sealey Oct. 20, 1953 

